Lava lake rarity below 10 is crashing the game on terrain building stage.

---- Minecraft Crash Report ----
// I blame Dinnerbone.

Time: 25.04.14 11:27
Description: Exception in server tick loop

java.lang.IllegalArgumentException: n must be positive
at java.util.Random.nextInt(Unknown Source)
at ayy.a(SourceFile:442)
at od.a(SourceFile:175)
at axr.a(SourceFile:859)
at od.c(SourceFile:104)
at net.minecraft.server.MinecraftServer.i(SourceFile:269)
at cim.a(SourceFile:94)
at cim.g(SourceFile:110)
at net.minecraft.server.MinecraftServer.run(SourceFile:367)
at mu.run(SourceFile:667)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

– System Details –
Details:
Minecraft Version: 14w17a
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.7.0_17, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 248626984 bytes (237 MB) / 343146496 bytes (327 MB) up to 1908932608 bytes (1820 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx2G
IntCache: cache: 1, tcache: 1, allocated: 12, tallocated: 92
Profiler Position: N/A (disabled)
Player Count: 0 / 8; []
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

-----------------------------------------------------------

Dungeons = 1 and water lake rarity = 1 (both individually) are throwing the following, but not taking down the game (must be exeption handler is set?)

[11:31:35 INFO]: Client> java.io.IOException: Stream Closed
[11:31:35 INFO]: Client> at java.io.RandomAccessFile.length(Native Method)
[11:31:35 INFO]: Client> at ayc.a(SourceFile:293)
[11:31:35 INFO]: Client> at ayd.close(SourceFile:234)
[11:31:35 INFO]: Client> at java.util.zip.DeflaterOutputStream.close(Unknown Source)
[11:31:35 INFO]: Client> at java.io.FilterOutputStream.close(Unknown Source)
[11:31:35 INFO]: Client> at ayf.a(SourceFile:148)
[11:31:35 INFO]: Client> at ayf.c(SourceFile:136)
[11:31:35 INFO]: Client> at bia.b(SourceFile:32)
[11:31:35 INFO]: Client> at bia.run(SourceFile:25)
[11:31:35 INFO]: Client> at java.lang.Thread.run(Unknown Source)